what I can remember:most of it played in a diner, where the murderer (female, young, black hair) falls in love with a guy.They were randomly meeting there and just talking (if I remember right)She kills (or poisons) unfaithful (I guess married) men in hotel rooms / apartments.Something about the black widow killer came to my mind, but nothing found through google I would place it probably around the 90sHope this little description helps Thx in advance!